The addition of magnesium sulfate and borax to urea reduced soil NH3 emissions but increased N2O emissions from soil with grass

Nitrogen (N) use efficiency can be increased by the addition of substances to urea. Magnesium sulfate (MgSO4) and boron were considered as plant nutrients, while zeolite was used as soil conditioner. The addition of these substances may affect soil NH3 and N2O emissions, by increasing N use efficiency. We conducted an 30 days incubation experiment with ryegrass using fertilizer treatments (12 g N m−2) as follows: urea (U); urea + MgSO4 (UM); urea + MgSO4 + borax (UMB); zeolite + urea + MgSO4 (Z-UM); and zeolite + urea + MgSO4 + borax (Z-UMB). We measured NH3 and N2O emissions and the aboveground N uptake of ryegrass. Cumulative NH3 emissions of UM, UMB, Z-UM and Z-UMB were 10%, 53%, 21% and 58% lower than U, respectively, while their N2O emissions were 32%, 133%, 43% and 72% higher than U, respectively. Aboveground N uptake of UM, UMB, Z-UM and Z-UMB were 9%, 6%, 12% and 13% higher than U, respectively. Overall, we suggest that the addition of MgSO4 and borax were effective in reducing NH3 emissions and potentially increase plant N uptake. However, the risk of higher denitrification and N2O emissions also needs to be considered. This study reveals the considerable effect of MgSO4 and borax in soil N cycles. Future research should evaluate how the application of urea + MgSO4 + borax effects gaseous emissions and crop yield of dicotyledons and in drier soil conditions.